1,721,009 research outputs found
Agri-food by-products and lactic acid bacteria as a strategy to improve the quality and functionality of “Primo Sale” cheese.
No full textIn Europe alone, 22.4 million tonnes of food by-products (BPs) are generated each year. However, they still contain valuable compounds, which can be valorised by the food industry. For this reason, some BPs have been selected to be used as ingredients for the production of “Primo Sale” cheese.
Orange peels (Citrus) and Equisetum arvense (Eq), a weed plant, were chemically and functionally characterised and used for the formulation (2 % and 1 % w/w, respectively) of “Primo Sale” cheese. Three functional Lactic Acid Bacteria (LAB) were also used in addition to the starters. The cheese samples were monitored over 29 days at 4 °C for the indigenous microbiota, starters’ viability, volatile compounds and antioxidant activity. Results showed that the addition of the BPs did not
affect the starters’ viability, which was higher than 8 Log units, while growth of spoilage microbiota was inhibited. Inhibition of Pseudomonas sp. was observed in the cheeses added with the LAB. Moreover, Citrus and Eq had a synergic effect resulting in 2 Log units lower than the control with LAB. Antioxidant activity of the cheeses increased with the addition of both BPs compared to the controls, with the best results observed for the Citrus-added cheeses. Furthermore, all the matrices showed a significant increase of the antioxidant activity over time (p<0.05),
doubling at the end of storage. The analysis of volatile compounds showed that the content of the organic acids increased overtime for the samples with the presence of residues, and particularly for short-chain fatty acids. In conclusion, the addition of BPs to the cheeses positively impacted the shelf-life without affecting the growth of the LAB strains. In addition, they improved certain properties such as the antioxidant one and allowed differentiation in the volatile profile. Finally, the use of these substances can increase the prebiotic effect and fibre content
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Insights into the mechanism of oxidative deamination catalyzed by Dopa decarboxylase
No full textThe unusual oxygen-consuming oxidative deamination reaction catalyzed by the pyridoxal
5′-phosphate (PLP) enzyme DOPA decarboxylase (DDC) was here investigated. Either wild-type or Y332F
DDC variant is able to perform such oxidation toward aromatic amines or aromatic L-amino acids,
respectively, without the aid of any cofactor related to oxygen chemistry. Oxidative deamination produces,
in equivalent amounts, a carbonyl compound and ammonia, accompanied by dioxygen consumption in a
1:2 molar ratio with respect to the products. Kinetic studies either in the pre-steady or in the steady state,
together with HPLC analyses of reaction mixtures under varying experimental conditions, revealed that
a ketimine accumulates during the linear phase of product formation. This species is reactive since it is
converted back to PLP when the substrate is consumed. Rapid-mixing chemical quench studies provide
evidence that the ketimine is indeed an intermediate formed during the first catalytic cycle. Moreover,
superoxide anion and hydrogen peroxide are both generated during the catalytic cycles. On this basis, a
mechanism of oxidative deamination consistent with the present data is proposed. Furthermore, the catalytic
properties of the T246A DDC mutant together with those previously obtained with H192Q mutant allow
us to propose that the Thr246-His192 dyad could act as a general base in promoting the first step of the
oxidative deamination of aromatic amines
Tat-mediated delivery of human alanine:glyoxylate aminotransferase in a cellular model of Primary Hyperoxaluria Type I
No full textDefects in liver peroxisomal alanine:glyoxylate aminotransferase (AGT), as a consequence of inherited mutations on the AGXT gene, lead to primary hyperoxaluria type I (PH1), a rare metabolic disorder characterized by the formation of calcium oxalate stones at first in the urinary tract and then in the whole body. The curative treatments currently available for PH1 are pyridoxine therapy, effective in only 10–30 % of the patients, and liver transplantation, an invasive procedure with potentially serious complications. A valid therapeutic option for PH1 patients would be the development of an enzyme administration therapy. However, the exogenous administration of the missing AGT would require the crossing of the plasma membrane to deliver the protein to liver peroxisomes. In this study, we constructed, purified and characterized the fusion protein of AGT with the membrane-penetrating Tat peptide (Tat-AGT). Although Tat-AGT shows subtle active site conformational changes as compared with untagged AGT, it retains a significant transaminase activity. Western-blot analyses, enzymatic assays and immunofluorescence studies show that active Tat-AGT can be successfully delivered to a mammalian cellular model of PH1 consisting of chinese hamster ovary cells expressing glycolate oxidase (CHO-GO), whereas untagged AGT cannot. Moreover, the intracellular transduced Tat-AGT makes CHO-GO cells able to detoxify endogenously produced glyoxylate to an extent similar to that of CHO-GO cells stably expressing AGT. Altogether, these results show that the Tat peptide is capable of delivering a functional AGT to mammalian cells, thus paving the way for the possibility to use Tat-AGT as an enzyme replacement therapy to counteract PH1
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Reactions of human liver peroxisomal alanine:glyoxylate aminotransferase with beta-chloro-L-alanine and L-cysteine: Spectroscopic and kinetic analysis
No full textIn addition to the main transaminase reaction, the pyridoxal 5'-phosphate-dependent enzyme human liver peroxisomal alanine:glyoxylate aminotransferase (AGT) is able to catalyze the alpha,beta-elimination of beta-chloro-L-alanine with a catalytic efficiency similar to that of the physiological transaminase reaction with L-alanine. On the other hand, during the reaction of AGT with L-cysteine, changes in the coenzyme forms and analysis of the products reveal the occurrence of both beta-elimination and half-transamination of L-cysteine together with the pyruvate transamination. A mechanism in which a ketimine species is the common intermediate of half-transamination and beta-elimination of L-cysteine is proposed. L-cysteine partitions between these two reactions with a ratio of approximately 2.5. Rapid scanning stopped-flow and quench flow experiments permit the identification of reaction intermediates and the measurements of the kinetic parameters of L-cysteine half-transamination. The k(cat) of this reaction is 200- or 60-fold lower than that of L-alanine and L-serine, respectively. Conversely, L-cysteine binds to AGT with a binding affinity 30- and 200-fold higher than that of L-alanine and L-serine, respectively. This appears to be consistent with the calculated interaction energies of the L-cysteine, L-alanine and L-serine docked at the active site of AGT
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